When Quantity and Quality

of Vision Don’t Add Up

The frustrating visual demands of presbyopes and the challanges of soft multifocal lens fitting



Stephanie Ramdass OD MS MBA FAAO

Private practice in Toronto (CA)

Adjunct faculty member Michigan College of Optometry (US)

Introduction 

For our patients fit in off-the-shelf multifocal lenses, it can be frustrating for both patient and eye care professional when the 20/20 vision recorded in-office is overshadowed by poor performance of lenses out in the “real world.” High-contrast letters used in the exam lane can often be identified by patients, but the crispness of vision may be lacking. Can we improve our contact lens fits to better satisfy our patients’ visual needs?

Investigating a Potential Solution

A randomized, single-masked study carried out by investigators at Michigan College of Optometry’s Vision Research Institute evaluated what effects offset multifocal optics, in relation to subject's visual axis, or line of sight, had on overall success of soft multifocal contact lens wear. During the initial visit, topography was performed overtop SpecialEyes 54 Multifocal contact lenses in hioxifilcon D material. The distance from the visual axis to the approximate center of near optics was measured using the instrument’s built-in software to determine the mismatch between the two points. Two pairs of lenses were ordered, one with geometrically centered optics and the other with optics displaced nasally 1.0 mm. 

Using Everyday Targets

During the follow-up study visit, LogMAR visual acuity at both distance and near were recorded for both the centered and offset optics lens pairs. Additionally, each subject rated their binocular distance and near visual acuity as well as their ability to view the following specific targets held at set distances: an article in a magazine, an email on a cell phone and usage instructions on an eye drop bottle.

 Fig 1 - Topographical analysis revealed that 100% of study lenses manufactured with geometrically centered optics showed temporal displacement of optics in relation to each subject’s visual axis

Study Results

Topographical analysis revealed that 100% of lenses manufactured with geometrically centered optics showed temporal displacement of optics in relation to each subject’s visual axis (figure 1). While there was no statistically significant difference (SSD) in LogMAR acuity for distance viewing and only slight SSD when viewing targets at near, the most noteworthy improvement was observed in subjective responses when viewing various targets, with 19 out of 20 subjects who completed the study favoring the lens pair with 1.0 mm nasal offset optics, despite the clinically insignificant difference in acuity measurements. 

Clinical Takeaways

Under normal foveal fixation, a patient’s line of sight is located nasal to the pupillary axis. A lens that is designed with optics to center perfectly over the pupil will naturally not align perfectly with a patient’s line of sight. Our study showed that when multifocal optics are nasally displaced to better align with the apparent location of line of sight, nearly all subjects experienced an increase in the subjective quality of their vision. Overlapping or doubling of letters, 3D effect, or halos around print were noticeably reduced as per subject commentary. 

Perhaps it’s time for us to think outside the “box” and fit our patients in multifocal lenses that are more specifically customized for their ocular features. 

Stephanie Ramdass is in private practice in Toronto, Canada and is an adjunct faculty member at the Michigan College of Optometry. You can reach her at StephanieRamdass@ferris.edu

She has received travel funding from Paragon Vision Sciences and lecture honoraria from Wink Productions, Inc. and Bausch + Lomb